Method for making tubes



March 11, 1941, QUARNSWQM 2,234,450

METHOD FOR MAKING TUBES- Filed Oct. 14, 1938 2 Sheets-Sheet 1 ATTORNEY 3 Ema, ww

r B. L. QUARNSTROM METHOD FOR MAKING TUBES March 11,1941.

Filed Oct. 14, 1938' t 2 sheets-she 2 INVENTOR. fiert LQuarn stro 1 m; w, W 4

82 ATTORNEYS Patented Mar. 11,1941

UNITED STATES PATENT I tm'rnon-ron me mass osrics But 1.. qumh-eh neimia Mich am" a Bnndy Tubing Company, Detroit, Mich, a corporation of Michigan Application October 14, 1938. Serial No. 235,052 3 Claims. 1 (Cl. 113-33 This invention relates to a method for making tubing from strip metal stock; and ithas to do particularly with themaking. oi .plural p ytube. from a plurality of .strips stock.

! p The invention may be exemplified by a description oi the making of double ply tube] from 'twostrips of stock. One strip which may form the inner ply or the tube, is moved longitudinall and is fashioned into tubular form with a longitudinally running seam. The edges 01' the stri 'arebrought together at'the seam, and the edges may be brought together in abutting relationship; In order to keep the edges together, prior to ultimate completion of the tube, the 1,5 inner strip is so fashioned that the metal, measured circumferentially. is slightly in excess 0! that required to complete the tubular form, and

when the edges areurged' into abutting relationship the metal is stressed. This stress holds the edges in closely abutting relationship. The other strip, which may form the. outer ply, is moved longitudinally with likemovement, and is iashioned into tubular shape around the tubular form 0! the inner ply. The strip -ior the outer ply is as so bent or fashioned that certain portionsare given a curvature, on a'radius. shorter than" the radius which is taken in the'completed tube; and in sucha manner that theiedge' portions oi? the outer ply: irictionally'gripthe inner ply so that so; the edges oi'the outer ply remain in proper seam forming relationship prior to the ultimate secur-' ing of the edges and piles together. with the tube thus formed. the seams and plies are united by a metal which is rendered molten. 33 -Inthe drawings:

Fig. 1 is a view illustrating, somewhat diagrammaticaliy, an apparatus and a method for mak-' ing tubing in accordance with the invention. g. 2 is an enlarged crosssectional view of the yeti-i for forming the inner 'tially on the line 2-2 of Fig.

,Fig. 3 is an enlarged cross sectional view taken.

substantially on line of Fig. 1, showing the iirst'iorming operation onthe inner strip..- Fig. 4 is an enlarged viewtaken substantially on line H of Fig. 1, the second torming operation on the inner strip." a Fig. 5 is an enlarged sectional view taken substantialiy' .on line H "of mg. .1, showing the -third-' iormin operation or, the inner strip.

substantiallyon line H me. 1, showingthe fourth torming operation on the inherstrip.

Flg.7isanenlargedsectionalviewtakensub as; stantially on line '|''i of Fig. 1, showing the iiith and final forming operation on the inner strip.

Fig. 8 is an enlarged sectional view taken substantially on line 8-! 0! Fig. 1 showing a preliminary operation which may be periormed'on the outer strip. 5 Fig. 9 is an enlarged sectional view taken substantially on the line l-l of Fig. 1 showing the first forming operation on the outer strip.

' Fig. 10 is an enlarged sectional view taken substantially on line il-ili of Fig. 1 showing the 10 second forming operation on the outer strip;

Fig. v11 is an enlarged sectional viewtaken sub- 1 stantially on lineii-ii 01' Fig. 1 showing the final forming operation.v I a Fig. '12 is an enlarged composite view 111113-15 trating the several forming operations on' the inner strip, said view being of sectional nature but with some parts not cross hatched for the purpose oiclearness.

Fig, 13 is an enlarged composite view similar go to- Fig. 12 showing the several forming operations on the-outer strip.

'1. The strip stock from which the. tube is made may be ferrous metal which is coated or plated with a sealing metal such as-low or high fusing point solder, as' for example, a solder. comprisinglead and tin or a solder comprising euprous' metal. Other sealing metals or solders maybe used as longas the solder or sealingemetai :melts or iuses at a temperature lower 'thansthat" of so the strip. Also, other metals may be used in the v strip. e The strip stock i. which forms the inner ply, may be drawn from a reel: and it is passed through a tube mill comprising a series of form- 'ing rolis. The first set oi rolls 3, as shown here- It in, forms thestrip into a rather open U-shaped form: as shown in Fig. 3. The second set of rolls '4 continues this ,iorming as shown in Fig.4. The

ply, taken substanthird set oi rofis 8 iurther progresses theiorming or the strip substantially into .u-shape, as shown in Fig. 5. The bight portionsot the form shown in Figs. 3, 4 and 5 are on a radius substantially-thesame as the radius upon which this .por-' tube. nie next set of rolls shown at I closesin Pa ition on-the inner stripasshowninFig.7.,. Fig. 8 is an enlargedsectionai view taken tion 0! the metal which will He ll i. the finished the u form as shown in Fig. 6, preferably leaving the edge portions 01' the strip substantially straight. 'l'li'enextsetoi'rollslbringstheedge portions together and completes the forming 'op At point it is thought well to describe the forming operations on the outer ply and to .then revert to a detailed description or the 'particuiarshapewhichisgiventotheinnerply and the outer ply may be drawn from a reel 2i and,. as shown herein; is passed between pressure rolls 8 which bevel the edges of the strip, as illustrated at 22 (Fig. 8). The outer strip may then be directed over a guide roll 23 and through a die 24, the formed inner ply also passing through this die. The formed inner ply and the outer strip then pass through forming rolls; one set of rolls is shown at 9, which performs an operation on the outer strip giving it a shape substantially. as shown in Fig. 9. The formed inner strip and outer strip then pass between a set of rolls l0 which may be placed on axes perpendicular to the axes of the rolls thus far descrlbedand fashion the edge-portions of the outer ply to a position, as substantially illustrated in Fig. 10. The formed inner ply'and the outer strip then pass between a set of forming rolls ll similar to Fig. 10, which completes the forming operation of the outer ply, as substantially illustrated in Fig. 11.

Thus a tube is formed from two strips of stock having double ply walls with the inner ply having its edges disposed .in a butt seam 25 and with the edges of the outer ply in a scarfed seam 26. The particular type of seams may vary as, for example, the edges for the outer ply may be arranged in a butt seam, but the preferred arrangement is that the seams be as shown herein. The composite tube structure may then pass through a series of rolls i2, I3 and it which may apply pressure to thetube structure. It will be understood that some of the rolls of the tube mill and some of the pressure rolls may be driven in order to propel the strips. and tubular form there- 'through. The number of forming rolls used on the inner strip and on the outer strip may vary,

thus varying the number of forming steps, as

such variations may be desirable or necessary with strip stock of various metals, thicknesses, widths, etc.

The tube may then be completed by a heat treatment to melt the coating dr plating metal and cause the same to fuse and thus unite the plies and seams. Such an arrangement is diagrammatically illustrated in Fig. 1 where electrodes i5 and I6 are connected to one side ll of a transformer for the heating current, and electrodes 8 are connected to the other side of the transformer. With this arrangement there is no potential between the outside electrodes l5 and IS, with the result that current flows through the section of tube between electrodes i5 and i8 and between electrodes l6 and I8. Since there is no potential between electrodes [5 and 16, the remaining part of the apparatus such as the tube mill and pressure rolls, need not be insulated. This is but one manner of heating the tube; other heating means such as furnace structures may be used through whichthe tube may be passed. It is within-the invention to carry the sealing metal into position in a form other thanthe form of a plating or coating on the strip stock itself'although so far as this disclosure is concerned, it appears sufllcient to make specific reference only to this one manner of carrying the sealing metal into position. It will be understood that'after the tube is heated for the fusing of the sealing metal'that it is properly cooled and, if neee'ssary, the tube may be confined in a neutral or reducing atmosphere while in heated form. I

.A problem inthe making of a tube of this character is that of maintaining the edges of the strips tightly together prior to the sealin of the tube with molten metal and also in maintaining the inner and outer plies in engagement with each other.

In Fig. 12, the several shapes assumed by the inner ply are shown and particular reference is made to the shape of the strip in that form shown in Fig. 6. In this condition the portions of the strip adjacent the edges are substantially straight although they may have some curvature. The radius of the curvature, however, from substantially the points a: to the points 1 is less than the radius taken by this portion of the metal in the finished inner ply. Accordingly, when the strip is in the shape shown in Fig. 6, the metal on each side of the form from substantially the point 1/ to the point x, as well as some of the straight metal beyond the point 1:, lies radially inwardly of the position which this metal is to assume in the finished inner ply. Therefore, when the edges of the strip are brought together in abutting relationship, as illustrated in Figs. 7 and 12, the metal of the strip is placed under stress. This stress causes the edges to come into close abutting relationship under pressure and are held in engagement by the force exerted by the stressed metal. As a result, the inner ply is self shape retaining and the abutting edges remain in abutting relationship so as to properly receive the molten metal which will flow between the edges and seal the same. In other words, the situation may be viewed as one where the over-all distance from the points y to the edges, while .in the Fig, 6 form, is greater than that required from the points 3/ to the butt seam to complete the formation of the inner ply into the form shown in Fig. '7.

The first forming operation on the outer strip, as indicated in Figs. 9 and'13, places a curvature in the strip where the strip overlies the butt seam of the inner ply, and from about the pointsa to the points or edges 6 of the strip, the stock is given a radius somewhat less than the radius this stock will assume in the finished tube. The

intermediate portions between the curved form in the center portion of the outer strip and the points a, may remain rather straight. The rolls I0 then fashion the outer strip inwardly, as illu'strated in Figs. 10 and 13, and in Fig. '13 it will be note'dwith clearness, how the portions from a to b are formed on a radius shorter than that of the finished tube. The center of the tube is illustrated at 0 while the centers of curvature for the sections from a to b are illustrated at d and e. Accordingly, the extreme edge portions of the outer ply lie, in the Fig. 10 position, closer to the outer periphery of the inner ply than do the intermediate portions between points a and b. The rolls ll then engage the outer ply and complete the fashioning of the outer ply urging the beveled edges into the scarfed seam 2B. In doing this, the metal between points a and b which is formed on the somewhat smaller radius, is straightened somewhat onto a larger radius. Thus the 'metal is stressed, causing the portions of the outer ply adjacent its edges 1 to frictionally grip the inner, ply with a force caused by the stress in the metal. The edge which is innermost of the scarfed seam frictionally engages the formed inner ply to its extreme edge; the edge which is outermost of the scarfed seam frictionally engages the metal of the inner ply from a point beginning at the end of the, bevel. Also, the stress on the metal causes the beveled surface which is outermost of the scarfed seam to tightly abut against the beveled surface on the other edge.

Thus a tube is formed from two strips of stock wherein the strip forming the inner ply is self shape retaining, with its edges maintained in engagement by stress in the metal, and wherein the strip forming the outer ply is self shape retaining, the stress in the metal holding the outer ply contiguous to the inner ply substantially throughout the circumferential extent and holding the edges in tight engagement by the force exerted due to the stress in the metal. The tube thus formed is capable of maintaining its own shape during that temporary time between the completion 'of the forming of the tube and the time when the sealing metal unites the plies and seams. It will be appreciated, of course, if the plies or seams are not close together that the sealing metal will not properly unite and seal the same.

I claim:

1. The method of making plural ply tube from a plurality of strips of metal stock wherein the plies and seams are united by fused sealing metal; the steps comprising fashioning'one strip into an inner ply of hollowcross sectional form, fashioning and setting portions of an outer strip adjacent its edges, on radii shorter than the radius of the outer ply in the finishedftube, fashioning the outer strip around and contiguous to the inner ply with pressure to stress the metal of the outer ply incident to the resultant increase of the said radii of curvature of said portions, which stress causes the edge portions of the outer strip to frictionally engage the inner ply, whereby-the outer ply is self shape-retaining upon the inner ply.

2. The method of making plural ply tube from a plurality of strips of .metal stock wherein the plies and seams are united by fused sealing metal;

the steps comprising fashioning one strip into an inner ply of hollow cross sectional form, with a longitudinally extending seam, fashioning and setting the edge portions of an outer strip, which is to form an outer ply, on radii shorter than the radius of the outer ply in the finished tube, fashioning the outer strip around the inner ply and bringing the edge portions thereof into seamforming relationship at a point circumferentially removed from theseam of the inner ply, to stress the metal of the outer ply incident to the increase of said radii of curvature of said edge portions, as the said portions so curved are brought into contiguous relation with the inner ply, whereby the stress in the metal causes the edge portions of the outer ply to frictionally grip and to remain fixed upon the inner ply..

3. The method of making plural ply tube from a plurality of strips of metal stock wherein the plies and seams are united byifused sealing metal; the steps comprising fashioning one strip into an inner ply of hollow cross sectional formybeveling' the edgesof a strip for forming the outer ply, fashioning and setting portions of said outer strip adjacent its edges on radii shorter than'the radius of the outer plyin the finished tube, fashioning the outer strip around and contiguous to Ply.

BERT L. SI'ROM. 

